1. This invention is directed to a system for applying a protective coating to the surface of a wide range of wares that include housewares, the system including applying a protective coating over decorative material that may also be applied in accordance with the present invention; and to the wares produced thereby. The wares include frangible articles for food and drink, and a wide variety of other articles.
2. An extremely wide range of articles currently in use are susceptible to being damaged and made less useful by impact damage and surface wear. Also, the processes used in decorating such wares are frequently slow, labour intensive and costly.
Widespread use is presently made of tableware of frangible materials such as glass, china, and clay; also, stainless steel is used for serving dishes, while cutlery may be of stainless steel, or plated with chromium or even gold and silver. Such wares are in need of improved protection and lower cost decoration.
Glassware can be manufactured at low cost, is hard-wearing, sanitary, and readily washed, but is extremely frangible, and fractures with sharp edges. China wares are more expensive, but have similar characteristics to glassware. Clayware (pottery) is usually weaker than glassware, but is somewhat less dangerous when broken. This group of wares are in need of protection, to increase their strength, and to reduce the danger presented when they fragment.
The decoration of these wares is relatively expensive and somewhat limited.
In the case of articles associated with human consumption of food and drink, the available pigments that can be safely used are severely limited in number. Glass can be batch-coloured, in the melt, prior to being cast.
Surface-applied colours are legally restricted to a limiting class of non-toxic colouring materials.
Surface decorations of glass and ceramics, other than by hand-painting, are presently applied by screen printing or the use of decals, which may be preprinted on a paper or plastic film.
The inks generally need to be inorganic, in order to withstand the high firing temperatures required to fuse the coloured frit.
In the case where a ground glass frit serves as the base, this limits the quality of the print.
The screen printing process is labour intensive, as each colour of the design requires individual application, with associated high costs for screen making and set-up, while time requirements tend to be excessive.
Decals are generally applied by hand, as they usually require precise visual location. The products are then hand-loaded into a 1200 F. degree furnace, to fuse the decoration, and subsequently unloaded by hand.
The existing processes are slow, expensive and labour and energy intensive, and do not lend themselves to automation. Also, the required production facilities are both extensive and expensive.
The present invention provides a protective and decorative system applicable to a wide variety of wares, including wares associated with the handling and consumption of food and drink, that are subject to FDA regulation.
Considering first the protective aspect of the subject process, as it applies for instance in the case of drinking glasses or tumblers.
Using the subject process, the fracture-resistance factor (xe2x80x9cfrac-Rxe2x80x9dxe2x80x94resistance to fracture) of a tumbler can be increased as much as tenfold in some instances, compared with the uncoated article, by the application of a relatively thick protective coating forming part of the present invention.
Alternatively, the frac-R can be increased by a more modest factor of say three to four, but with an associated improvement in the fragment-retentability characteristic of the coating, such that when fragmentation occurs, the dispersion of glass particles and shards is significantly limited.
The desired compromise between these two protective aspects can be predetermined by precise control of the thickness of the protective coating, which control is made possible by the present process.
The application of a first adherent coating to a glass surface, in accordance with the present invention facilitates the application of decoration to that surface. The coating is formulated such that, when cured, it accepts the adhesion of printing inks to its cured surface. A further protective coating of non-toxic plastic can then be applied, to encapsulate and hermetically seal the decorated surface.
One embodiment of the subject process employs flow-coating to apply one or more of the coatings. Such coatings may include tinting colours, to give the appearance of coloured glass. The tinting colour may be integrated with the first, adherence promoting coating.
This encapsulation of the applied decoration enables the use of organic colouring materials that would previously have been unacceptable from a health and safety point of view.
The subject coating process may be used in combination with many modes of printing, including a variety of digital printing processes, particularly Digital Ink Jet (DIJ) printing.
In one aspect of the present process, transfer of material to an article may involve a pad printing process.
Application by way of the present process of the subject coatings enables decorative and printed matter to be applied to an extremely wide range of materials that formerly were not readily printed upon.
The subsequent application of a bonded, protective clear coating can then hermetically seal and protect the applied decorative matter.
Such protective coatings are usually tougher than the undercoating, with a hard, abrasion resistant outer surface.
It will be understood that the terms xe2x80x9cdecorationxe2x80x9d and xe2x80x9cdecorative matterxe2x80x9d encompasses prosaic matter including warning notices and other text, as well as including the application of a full colour coating.
In the case of glasswares, the subject process enables the direct application of printed material to an initially plastic-coated glass surface.
In the case of items such as flatware that normally is subject to deterioration in appearance, such as the oxidation of silver, or the wearing off of silver and gold plating, or the deterioration and wear of gold ands silver articles, the application of the subject protective coating can isolate such vulnerable surfaces from oxidation and wearing contacts.
The clear nature of the available coatings renders them virtually visually undetectible to the naked eye.
For other wares having coloured, decorated or marked surfaces that are susceptible to wear or damage, the application of the subject protective coating can greatly extend the effective life of such wear-susceptible surfaces.
The subject protective coating may be an essentially water based plastic composition, preferably incorporating an adhesion promoter which promotes bonding of the coating material to the surface being coated.
Selection of coatings, for either printing upon or as an outer, protective coating is determined by the desired qualities such as Food Use approval, impact resistance, dish washer safe, surface wear resistance (hardness and toughness); etc.
In the case of an undercoating, such as a urethane, selected to receive print material (e.g. ink adhesion), the undercoating may also be selected based upon the degree of adhesion thereto of a selected protective outer coating. Furthermore, the undercoating may incorporate a background colour, usually white, to serve as a base or background for any applied decoration.
Thus, in the case of coatings being applied to receive decoration, the coating material, such as a urethane coating, is formulated to accept the decorative inks or other media that will be applied, and also to accept a hard outer coating in close-bonded relation thereto.
As an alternative to an adhesion promoting element incorporated with the undercoating, a separate adhesion promoting undercoating may be applied, prior to the application of the print-receiving undercoating (for decoration) and/or other coatings.
The respective coatings are preferably cured with ultraviolet light (u.v). In the case of the outer surfaces of drinkware, this involves the use of xe2x80x9cfood contact approvedxe2x80x9d u.v. coatings.
The range of u.v. cured protective outer coatings extends to include, but is not limited to polyesters and other polymers, polyurethanes and acrylates having the desired visual and protective qualities, and being effective in some instances at raised temperatures, some in excess of 300 F. degrees.
The adoption of the low-temperature ultra-violet (u.v) curing process makes the subject coating and decorating process applicable to plastic wares, including many thermoplastics, as well as other temperature sensitive materials, including paper, wood and many composites.
In some instances, for materials such as some plastics, an initial coating to accept ink may not be required, enabling the desired decoration to be applied directly to the surface of the plastic, as by DIJ.
In the case of glassware such as drinking glasses that are to be decorated, an initial thin printable undercoat such as urethane is applied, by flow-coating or possibly by DIJ, to a thickness in the range 0.5 to 1 mil (0.0005-0.001 inches), and u.v cured. The glass can then be printed directly by way of DIJ printing, or indirectly by transfer pad.
For flat articles, such as flatware, roller coating may be employed, in combination with u.v. curing.
Decoration can then be applied, using coloured inks if so desired, by a printing process such as digital ink jet (DIJ) printing. In some instances the decoration may be applied directly to the article.
In instances where a number of colours are involved, these may be individually applied in successive imprints, with u.v. curing after each imprint in some instances. Pad transfer may be employed both on the application of colour printing and/or coatings and for protective outer coatings.
For example, an article may be initially imprinted with a selected (frequently light) background.
The first step of decorating, such as by way of applying printed matter, is to define the precise location, shape and size of the decoration to be applied, by applying a background colour to cover the precise decoration area. This background colour is usally white, being a neutral colour, so as not to adversely affect the colours specified for application in the decoration, which will be applied on top of the background.
The artwork is based upon the designer""s xe2x80x9cBit Map Imagexe2x80x9d [BMI], which defines the respective areas for the application of the individual colours that will constitute the final art work.
For instance, on the basis of a designer""s BMI, with a specified process colour as an example, a sequence of Cyan, Yellow, Magenta and Black would each be individually printed.
Each individual colour printing would be on the precise areas programmed in the BMI for that colour.
DIJ printers lend themselves ideally to this use, being enabled by way of the present invention to print directly onto the subject article, with consequent improvements both in quality and in rate of output.
The end result is a full colour print, with the respective colours in precise registry, in accordance with the BMI.
Finally, a clear protective coat may be applied by DIJ printing in accordance with the present invention, to cover the decoration area, plus a predetermined border overlap, perhaps in the order of 0.0015 inches, to provide effective sealing of the decoration, both from a wear protection aspect of the decoration and to isolate the decorative pigment material where health requirements may be an issue.
Depending on the nature of the inks being applied, curing may not be necessary after each printing step. If so required, u.v. curing as disclosed herein provides many advantages.
The use of computer-controlled DIJ printers permit precise and ready changes such that changes to a processing line to accommodate different articles may be rapidly carried out, enabling high plant utilization, for a variety of products and decorations.
In the case of products such as ball point pens for instance, this represents a vast improvement over existing decorative processes.
Thus, a programmed design incorporating a number of different colours may be rapidly applied over a contrasting background, and receive a wear-resistant coating, in a single, short production line, using DIJ printing, with u.v. curing when required.
The application of an outer protective coating selected from the specified group of plastics may also be applied in the form of a water-based emulsion, by way of a flow coating.
A great many benefits accrue from the use of u.v. curable inks with DIJ printing. However, many of the aspects of the present invention may be applied for use with conventional DIJ inks, which do not require curing by u.v. radiation.
The outer coating can be in the order of 0.5 mil (0.0005 inches) and greater.
As u.v curing is a low temperature process, it may be used with thermally susceptible material such as paperware and plastics, including foamed plastic, and plastics that are heat shrinkable.
This capability may be combined in many instances with several varieties of DIJ printing, in the decorating and protection of an extremely wide range of products.
The adoption of u.v. curing usually implies the need for controlled ventilation, in view of the generation of fumes and vapour of limited toxicity.
With flow coating using water-based coatings, even foamed plastic bodies can be coated and decorated and/or printed upon, including the application of durable protective coatings.
In the case of decorating ceramic mugs, where fracture resistance is not a major consideration, an outer coating of 0.5 to 1.5 mil forms an adequate hermetic seal for an applied decoration, while providing effective abrasion and dishwasher (commercial type) protection.
For beverage glasses, where fracture resistance is more critical, a much thicker coating is preferred.
From experimental work with a urethane outer coating on beverage glasses, a 5-mil urethane coating provided a frac-R factor of ten or more, the coated beverage glass being at least ten times more break resistant than an unprotected beverage glass.
Upon breakage, the thus coated glass composite tended to break into large chunks.
The use of u/v curing, combined with coating materials having a very high solids content enable the achievement of significant coating thickness, as much as five to six mil (0.005-0.006 ins.) in a single pass.
It will be understood that the subject outer protective coating is substantially dishwasher-proof, in that commercial dishwashings in excess of thirty cycles fails to mar the finish or have any apparent affect on its adhesion and durability.
The coating may be transparent and present a bright and sparkling appearance, as to be visually substantially undetectable to the naked eye.
The adoption of flow coating with aqueous based coating materials enables high material utilization, with recycling of excess and spillage material, for an economically competitive product and process.
The substantial avoidance of organic solvents provides a process that is both economical and ecologically friendly, while extending the range of protectible materials, which can include foamed plastics that would be susceptible to damage from organic solvents.
The low temperature characteristics of U.V. curing furthers its use with temperature sensitive objects.
The above described characteristics enable the application of coatings for both wear and decorating upgrades to a wide field of items, including items of household and personal use, by way of high speed automated processes, thus enabling competitive pricing in the market.
Such coatings may be decorative, or clear and primarily protective. Decoration would normally also be protected with a hermetic protective overcoat. In some instances, the decoration may be plain colour.
As a further benefit, the adoption of low temperature curing by way of U.V. curing has a markedly beneficial effect on plant start-up capital requirements, as the U.V. curing is extremely rapid, with a physically short cure section, while the need for a cooling tunnel (as much as 30 feet long) in the process line, that would be required for thermal curing, is substantially eliminated, with considerable cost benefit, including diminished building size requirements.
The subject process is extremely flexible. As a for-instance: a clear or coloured primer coat, which may include an adhesion promoting component, may be applied by transfer pad to a predetermined surface area which is to be decorated, and the primer cured by u.v. light.
Such a surface may be planar or curved.
The decoration may then be applied to the prepared surface, by methods that may include DIJ printing, and variants thereof, such as pad transfer.
A protective coating that extends beyond the decoration may then be applied and u.v. cured, thus encapsulating and in most instances hermetically sealing in the decoration.
In some applications one or more of the coatings may be applied by roller coating, being particularly applicable to flat articles.
In other instances spray coating or dip coating may be utilized. Thus, bowls that are not suited to rotation upon a mandrel may be spray coated, and dip coating may well be applied to scratched bulk articles such as beer bottles, to extend their useful service life.
The printing modes used for applying decoration may include DIJ printing for a wide range of coloured inks, while ceramic inks incorporating inorganic pigments may be applied by screen printing.
The use of DIJ printing may be extended to include the application of surface coatings, such as protective, transparent coatings
The foregoing wide scope of coating and decorating methods enables protective coatings, print-receptive undercoatings, and encapsulating protective outer coatings to be applied to a wide range of article shapes, including right cylindrical, conical, flat and irregular surfaces, as well as localized or xe2x80x9cspotxe2x80x9d surfaces.
Furthermore, the subject processes are economical in terms of material utilization, speed and plant requirements.
A great many benefits accrue from the use of u.v. curable inks with DIJ printing. However, many of the aspects of the present invention may be applied for use with conventional DIJ inks, which do not require curing by u.v. radiation.
Some examples of wares that may be protected and decorated by the subject processes include:
Dinnerware and kitchen utensils including: glass, ceramic, plastic, pottery, china, porcelain, metal and composites in the form of plates, bowls, cups saucers, presentation plates, ornaments and figurines, etc;
Drinkware consisting of: mugs of ceramic, glass, plastic and metal;
wine goblets of glass and plastic;
tumblers of glass and plastic;
sport bottles and travel mugs of plastic
stainless steel travel mugs
Serverware including the above materials and also wood, as in trays, pitchers, bowls, plates, vases, candleholders, etc.
The range of products extends to include:
glass lamp shades, golf balls, coasters of ceramic, plastic and composites such as fiber-board; clip-boards, plaques, bag tags, metal name tags, promotional articles such as pens, pencils and rulers, waste baskets, timepiece faces and flowerpots and planters of pottery and plastic; and plastic foam articles such as insulator sleeves for beer cans, and utility items including mouse pads. Items such as these latter may have a protective outer plastic film laminated thereto.
The use of Digital Ink Jet printing lends itself to a range of surface applications, such that a wide variety of surface shapes may be accomodated.
DIJ printing can be applied directly to many surfaces.
In other instances where the shape of the object or the desired size of printed matter makes direct jet application impractical or uneconomic, pad printing may be used.
In one pad printing process, used for objects such as golf balls, the desired imprint is milled onto the surface of a steel plate precisely milled to the profile of the article being imprinted.
The profiled, imprinted plate is located in a pad printing machine and its surface is flooded with ink.
Excess ink is removed from the surface by way of a doctor blade, leaving just the engraved design in an ink-flooded condition. A shaped silicone pad is then applied to the engraved design, to transfer the inked design to the pad. The pad then is applied to the surface of the article, to tranfer the design to the article being imprinted.
In the case of glassware, the previously applied and cured plastic undercoat makes such transfer feasible.
In the case of DIJ printing, multiple colours may be applied simultaneously, thus obviating the former, unduly labour intensive work of re-indexing to the applicator the imprint area for each successive colour.
The jets of ink from a DIJ printing head may be directed onto a flexible silicone sheet, from which the ink pattern is then transferred to a convex shaped pad and applied by contact displacement to the desired printing area.
As referred to above, the imprinted area may have been previously prepared by the application of an ink-receptive undercoat.
Where the area of decoration is limited in size, or in accessability, the undercoat itself may also be applied by way of a transfer pad.
The rate of operation of a transfer pad sometimes exceeds the output rate of a DIJ printing head, such that a single transfer pad installation may serve a gang of DIJ printing heads, for enhanced output.
In some instances where an object, for instance a pen, has a decoration of limited size applied to the barrel, then an undercoat, if used, and the subsequent hard protective coating might employ transfer pads to apply the respective coatings. The undercoating, if required, will exceed the size of the decoration that is imprinted upon it, and the encapsulating outer coat will overlap the edges of the undercoat.
The transfer pads may be correspondingly selectively sized.
The use of roller coating may also be particularly suitable in some applications, in applying undercoats and protective encapsulating outer coatings.
For articles that can be mounted upon rotating mandrels, flow coating may be the preferred method for applying an overall coating.
In one embodiment for coating fairly thin planar articles,such as ceramic tiles, a digital ink jet printer may be used to apply both decoration and, in a separate DIJ machine or machines, any desired undercoat and/or outer protective coat may be applied. U.V. curing is readily provided, interposed between the serially arranged DIJ machines. In view of presently available DIJ machines of small size, such an arrangement may be provided as a process line located within an elongated fume cupboard, to deal with any fumes generated by the u.v. curing portion of the process.
In such an arrangement having a gang of two or more DIJ machines arranged in series, a common transfer belt may be provided, on which the articles are transferred between the serially arranged machines and through the intervening curing sections.
In such an arrangement, the capability of one machine to apply a protective coating may be used with the transfer belt itself, in an initial strengthening process, and in maintaining the belt as wear occurs.